This invention relates to a method of and an apparatus for winding coils such as stator coils of electric motor and more specifically to a method and an apparatus in which wires are wound on a coil former having a plurality of steps with increasingly larger size diameters, and in which the formed coils are dropped into a coil-inserting tool below the coil former.
As a kind of conventional method of and an apparatus for winding coils, there are examples of apparatuses which are disclosed in Japanese Patent Publication No. 18417/1982 and International Publication No. WO 82/02290.
In the above conventional apparatus, a coil former is composed of two divided coil formers each of which has a plurality of steps with increasingly larger size diameters and the divided coil former members are fixed to a support member capable of sliding up and down.
Around the coil former are provided four stripper rods which are capable of sliding up and down, respectively. A stripper plate is mounted radially at the forward end of each stripper rod. When each stripper plate is moved longitudinally downward in a gap formed in the coil former, the stripper plate transfers the formed coils on the coil former therefrom to the coil-inserting tool.
Outside the coil former is disposed a winding flyer which supports and guides a wire. When the winding flyer rotates around the coil former, a wire is wound on each step of the coil former.
Under the coil former is disposed a coil-inserting tool comprisiong a plurality of elongate angularly spaced apart blades of generally circular cross-section forming a cage. The coil-inserting tool receives the formed coils from the coil former and enables the formed coils to insert into a stator of an electric motor. When the coil former moves downward, the lowermost (first) step of the coil former enters slightly into the forward portion of the coil-inserting tool. In this state, upon the winding flyer beginning to rotate, a wire is wound on a first step of the coil former. During this operation, the stripper rods move up and down to push down each turn from the first step of the coil former toward the blades of the coil-inserting tool. The coil-turns pushed by the stripper rods go into gaps between the blades of the coil-inserting tool.
At a final stage of coil-winding on the first step, most of coil turns are inserted in the coil-inserting tool with a part of the coil-turns left on the first step of the coil former.
After a predetermined number of turns are wound upon the lowermost step of the coil former, the coil former moves downward by a length of the step of the coil former so that the second step of the coil former is located in a winding position where coil-winding on the second step is carried out. At this time, a leading portion of the final turn of the coil-winding on the first step is led onto the second step of the coil former. Thus, a winding operation on the second step is started and then most part of these coil turns are also inserted into the coilinserting tool with a small part of the turns left on the second step thereof.
In a similar operation, the coil turns on a third step and then coil turns on a fourth step and coil turns on the remaining steps are formed.
When a winding operation for a final step has been completed, the stripper rods are moved downward for a relatively long distance to their respective lowermost positions and parts of coils left on the respective steps of the coil former are inserted entirely into the coil-inserting tool. In this manner, a winding operation for a first pole of a stator is completed. Then, the leading end of the coils for the first pole is clamped by a clamping device and the coil-inserting tool is indexed at a predetermined angle in response to the number of poles to carry out the next pole winding operation. Thereafter, the coils for the next pole is formed in the above manner. The above operations are repeated to obtain the coils for a desired number of poles of the stator. After the completion of all winding operations necessary for one stator of a motor, a cutting device is actuated to cut the wire.
However, in this conventional method and apparatus, when the winding operation of a lower step of the coil former has been completed and then is transferred from the lower step to the next upper step, the transfered portion of the wire is caught in a step-like portion defined between the upper and the lower steps and is apt to slip on the step-like portion. This results in a drawback that a wire cannot be reliably transferred to a next step of the coil former at a given position without failure.
In view of the above described circumstances, in the prior art, when a winding operation is transferred from a lower step of the coil former to a next upper step of the coil former, the rotative speed of the winding flyer is decreased from 2,000.about.3,000 r.p.m. to 300.about.500 r.p.m. Instead, some technical experts tried to design the coil former so that its configuration can prevent catching of the wire at a border of two adjacent steps.
However, in these conventional apparatuses, it is impossible to secure a smooth transfer of the wire at a border of two adjacent steps, and the efficiency of winding operation is much decreased because the rotative speed of the winding flyer must be decreased when the winding operation is transferred.